The Repair Manual of SINOTRUK HOWO HC16 Drive Axle 1

1. STR-HC/ST16 Drive Axle

1.1. Structure and Principle of STR-HC/ST16 Drive Axle

STR-HC/ST16 Drive Axle is composed of final drive, differential, half axle and axle

housing. Its functions are shown as followings: ①To transfer engine torques from

universal driving devices to driven wheels through final drive, differential and half axle so

as to realize reducing speed and increasing torque. ② To change the direction of torque

transmission through cone gear pairs of final drive. ③ To achieve the differential effect of

wheels at two sides through differential so as to guarantee inner and outer wheels

steering with different speeds. In Figure 1-1, STR-HC/ST16 Drive Axle is composed of

final drive, differential, half axle and axle housing.

Final drive is one of major components in automotive transmission to reduce speed and

increase torque. When a transmission is not set with any overdrive gearing, the

transmission ratio of final drive shall be the minimum transmission ratio of driven system.

It can also be called as main transmission ratio. Differential is used to solve relevant

issues such as different rotation speeds of driven wheels at two sides in motor steering

and different speeds of multi-axis drive axle. Half axle is used to pass driving forces

reliably. Axle housing is an installation foundation piece of main components for

transmission and drive system.

In heavy duty truck, all drive axles are at the rear and called together as Rear Axle. Most

drive axles manufactured in SINOTRUK are double drive axles, and a few are single rear

ones. Normally, the front one of double drive axle is called as middle axle, and the rear

one as rear axle. Drive axles in SINOTRUK may be divided into two series such as STR

and HW according to their structural features.

                                          Figure 1 Composition of Drive Axle

1 – Clutch; 2 - Transmission; 3 – Universal Joint; 4 – Drive Axle; 5 – Differential; 6 – Half Axle

7 – Final Drive; 8 – Transmission Shaft

STR series drive axle is one of products with the largest output in SINOTRUK. It is an axle

being suitable to China's national conditions through ten years of digestion, absorption

and improvement depending on introducing Austria Steyr Technology. Its feature is to add

STR-HC/ST16.01

1st Edition 6

wheel reducer gears at central single-stage final drive. Therefore, the transmission of STR

series drive axle shall have double reductions and can also be called as double-stage

reduction axle. See Figure 1-2

                                               Figure 1-2 STR Series Tandem Drive Axle

As same as all drive axles, STR series drive axle is also composed of final drive,

differential, half axle and axle housing.

1.1.1. Final Drive

1. Central Final Drive

For rear final drive of STR series drive axle, see Figure 1-3.

                                                         Figure 1-3 Appearance

In Figure 1-4, the end flange of Flange 2 is connected with transmission shaft. There are

internal splines in its bore to fit with splines at the handle of Driving Bevel Gear 7 so as to transfer engine power from universal drive shaft to Driving Bevel Gear 7. Driving Bevel

Gear 7 can rotate around its axis under the support of two tapered roller bearings 4 and 6.

Driving Bevel Gear 7 and Driven Bevel Gear 9 can be a pair of mutually meshing bevel

gears. Their axes are perpendicular. Through their meshing, they can rotate the rotary

direction of above engine power with 90° and then transfer to Differential 15 installed

firmly with driven bevel gear. At the same time, any meshing between driving and driven

bevel gears can also reduce the power speed and increase its torque. Under the support

of Bearing 13 at two ends, Differential 15 may rotate around its axis to distribute engine

torque after speed reduction, torque increasing and commutation of driving and driven

bevel gears into two half axles.

                                       Figure 1-4 Structure of Final Driver

1 – Flange Nut .2 – Flange .3 – Oil Seal seat and oil seal assy. 4, 6, 13 – Tapered Roller Bearings 5 – Bearing Block 7 – Driving Bevel Gear 8 – Final Drive Housing 9– Driven Bevel Gear 10 – Adjusting Nut 11 – Round Nut 12 – Fixed Mesh Cover 14 – Seal Ring 15 – Differential Assembly

To guarantee proper meshing, the relevant position between driving and driven bevel gears may be adjustable. There is a group of adjustable washers (not marked in Figure1-4)

between counter-faces of Bearing block 5 and Final drive housing 8. That increasing and

reducing different thickness of washers make Driving Bevel Gear 7 and Bearing Block 5

move up and down together so as to adjust relevant positions of driving and driven bevel

gears in vertical direction. At the outside of Tapered Roller Bearing 13 at two ends of final

drive, there is one Adjusting Nut 10 respectively. That screwing in and out the nut may

make Differential Assembly 15 fastening with Driven Bevel Gear 9 move axially. The

adjustment in two above sections may adjust the mesh position of driving and driven bevel

gears to an appropriate state.

Before adjusting the above meshing state, smear red pigments (mixture of red lead

powder and oil) at tooth surface of driven bevel gear firstly, then use hands to make

driving bevel gear with reciprocating rotation. Therefore, there will be red blots at two

operating surfaces of driven bevel gear tooth. If any blot at forward and reverse operating

surfaces of driven bevel gear is at the middle of tooth height but inclined to little end as

well as is more than 60% of tooth width, it means the proper meshing. For proper meshing

blot, see Figure 1-5.

                                     Figure 1-5 Proper Meshing Blot of Driven Bevel Gear

The final drive housing of final drive assembly is opposite to the surface of axle housing.

Then, all including Axle Housing, Final Drive Housing 8, Bearing Block 5 and Oil Seal

Block together with Oil Seal Assembly 3, Flange2 and Flange Nut 1 will surround into an

enclosed space. In the space, there is a large amount of lubricating oil to lubricate moving

parts such as bearing and gear. In assembly, there shall be oil-resistant silicone sealant

between contact surfaces of final drive housing and axle housing, between contact

surfaces of final drive housing and oil seal block, between contact surfaces of oil seal

block and bearing block and between flange nut and flange to seal the lubricating oil

reliably in the space. That between oil seal block and flange shall be installed with oil seals

respectively for dust prevention and sealing oil so as to make flange rotate around its axis

under the support of bearing but also guarantee lubricating oil not penetrating from the

clearance between flange and oil seal block.

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